Allow removing lines using Dns class

lib/linux_admin/dns.rb

@@ -23,9 +23,9 @@ def reload
     end
 
     def save
-      contents = "search #{@search_order.join(" ")}\n"
-      @nameservers.each { |ns| contents += "nameserver #{ns}\n" }
-      File.write(@filename, contents)
+      search  = "search #{@search_order.join(" ")}\n" unless @search_order.empty?
+      servers = @nameservers.collect { |ns| "nameserver #{ns}\n" }.join
+      File.write(@filename, "#{search}#{servers}")
     end
   end
 end

spec/dns_spec.rb

@@ -14,6 +14,16 @@
 search new.test.example.com other.test.example.com
 nameserver 192.168.3.4
 nameserver 10.10.11.12
+DNS_END
+
+  NO_SEARCH = <<DNS_END
+nameserver 192.168.1.2
+nameserver 10.10.1.2
+nameserver 192.168.252.3
+DNS_END
+
+  NO_NAMESERVER = <<DNS_END
+search test.example.com test.two.example.com. example.com.
 DNS_END
 
   NEW_ORDER = %w(new.test.example.com other.test.example.com)
@@ -71,5 +81,25 @@
       subject.nameservers = NEW_NS
       subject.save
     end
+
+    it "omits search if the list is empty" do
+      expect(File).to receive(:write) do |file, contents|
+        expect(file).to eq(subject.filename)
+        expect(contents).to eq(NO_SEARCH)
+      end
+
+      subject.search_order = []
+      subject.save
+    end
+
+    it "omits nameserver if the list is empty" do
+      expect(File).to receive(:write) do |file, contents|
+        expect(file).to eq(subject.filename)
+        expect(contents).to eq(NO_NAMESERVER)
+      end
+
+      subject.nameservers = []
+      subject.save
+    end
   end
 end